1. Field of the Invention
This invention relates to a recording material having a recording layer which is thermally deformed by exposure to high intensity radiation.
2. Description of the Prior Art
Recording materials utilizing heat for image recordation are known. Information is recorded in these materials by exposing a recording layer to information-carrying high intensity radiation, such as laser light, to cause a certain thermal deformation, such as fusion, evaporation, aggregation or the like, to occur in the recording layer in the exposed areas due to the heat of the radiation used. Consequently, the optical characteristics in the thermally deformed areas of the recording layer are changed to form a visible image. Various techniques suitable for exposure using high intensity radiation applicable to a recording method using the thermal recording materials as described above can be employed. For instance, one technique includes the two steps of transforming the information to be recorded into electric time sequential signals, and scanning the recording material with laser light whose intensity is modulated by the electric time sequential signals; and another technique involves a two-dimensional exposure using a strobe light or a one-dimensional exposure of scanning with a laser light through a two-dimensional, optical information. In many cases, thermal deformation can be achieved in the recording materials merely by exposure to radiation for a very short time and, therefore, in general, post-treatments such as development are unnecessary for completing the recorded image because exposure to radiation is all that is necessary for completion of recording.
The recording layers of thermal recording materials as described above can be made of inexpensive metals, dyes, synthetic resins or other inexpensive materials. However, in order to obtain highly sensitive thermal recording materials, the recording layers thereof should be made of particular metals or should have various specific constructions. Various proposals for attaining such have been made. For instance, a recording layer of three layers, i.e., a germanium layer, a bismuth layer and a selenium layer, is disclosed in U.S. Pat. No. 3,560,994. In such a recording layer, the germanium layer lowers the reflectance, from the bismuth layer, of light used for exposure, and the selenium layer has a tendency to evaporate. Either factor described above accelerates the thermal deformation occurring in the bismuth layer corresponding to the main recording layer, and reduces the energy required for thermally deforming the recording layer, compared with the case where a bismuth layer alone is employed as a recording layer. Other layers provided on the main recording layer with the intention of further reducing reflectance or preventing reflection are disclosed in Japanese Patent Application (OPI) No. 151151/75 (The term "OPI" as used herein refers to a "published unexamined Japanese patent application".) and Japanese Publication No. 14263/76. Moreover, in order to decrease heat conduction from the recording layer to the support, a certain layer may be disposed between the recording layer and the support, as disclosed in U.S. Pat. Nos. 4,032,691 and 3,911,444. Furthermore, a double layer obtained by superposing a layer of a metal sulfide, a metal fluoride or a metal oxide upon a metal layer, or a single layer of a mixture of a metal and a metal sulfide, a metal fluoride or a metal oxide as a recording layer, which is disclosed in Japanese Patent Application (OPI) Nos. 78236/76 and 20821/77 has been used. Such being the case, it has been desired to discover recording materials having a sensitivity improved to such an extent that it is almost equal to or higher than the sensitivity attained using the various kinds of recording materials described above.